How can I upgrade my Mozilla Firefox 3.6.3 to the latest version for ubuntu?

I am using Mozilla Firefox 3.6.3 on my computer. But a message keeps coming while I use Firefox saying "You may want to upgrade your browser.
You're using an old version of Firefox that is no longer supported and may be insecure.
To upgrade, open Firefox's Help menu and click Check for Updates..."
But when I open Firefox's help menu, I can't see "check for updates" to click. What should I do?

I am using Mozilla Firefox 3.6.3 on my computer. But a message keeps coming while I use Firefox saying "You may want to upgrade your browser.
You're using an old version of Firefox that is no longer supported and may be insecure.
To upgrade, open Firefox's Help menu and click Check for Updates..."
But when I open Firefox's help menu, I can't see "check for updates" to click. What should I do?

Make sure that you meet the requirements for the current Firefox version.
*http://www.mozilla.org/en-US/firefox/20.0/system-requirements/
If you have a Firefox version from the Ubuntu repositories then you can't update Firefox directly, but can only do this via the Ubuntu update.
You can find the latest Firefox 20.0.x release in all languages and for all Operating Systems here:
*http://www.mozilla.org/en-US/firefox/all.html

Hjelpsomt svar

amitshree, the OP has a third-party build of Firefox from Ubuntu so there is no check of updates in Help menu as OP mentioned.

Yes the package dependencies could be a issue due to using the old Ubuntu 10.04 from April 2010 and especially because it is a LTS.

'''amitshree''', the OP has a third-party build of Firefox from Ubuntu so there is no check of updates in Help menu as OP mentioned.
Yes the package dependencies could be a issue due to using the old Ubuntu 10.04 from April 2010 and especially because it is a LTS.